The present invention relates to audio mixers, and particularly to an audio mixer architecture using virtual gain control and switching with a single active gain source in any one audio signal path that is controlled to provide both individual input gain control and overall master gain control.
Audio mixer architectures have traditionally had individual gain controls for each audio channel input to the mixer. The inputs in turn are combined to form various subcombination inputs that each have their own gain control, and finally the output of the mixer is controlled by a master gain control. For manual operation these gain controls have been in the form of variable resistors such as slides and potentiometers. However, in order to automate operation of an audio mixer, motorized variable resistors were used. This was a bulky alternative as well as producing unwanted noise in the audio signal path. With the advent of microprocessors some manufacturers have replaced the variable resistors with voltage controlled attenuators (VCA), the microprocessor providing the gain control voltage in response to the position of the variable resistors. VCAs in turn introduce noise and distortion into the audio path, especially when the gain is other than unity, that is cumulative as the audio signal passes through successive stages.
What is desired is an audio mixer architecture that has automatic capabilities without having successive stages of voltage controlled attenuators in the audio signal path.